This invention relates in general to furnaces for melting metals and more particularly to a regenerative furnace having an easily detached media box.
Some furnaces that supply molten metal for casting and other procedures utilize regenerative furnaces to improve efficiency. The typical regenerative furnace includes an enclosure having a hearth at its bottom for containing a molten metal, which is often aluminum. At one end of the furnace the hearth has tap holes for withdrawing the molten metal. At the other end the furnace has two ports located above the hearth, and these ports are connected to burner assemblies that operate alternately for supplying hot gases to the interior of the furnace enclosure—indeed, hot enough to maintain the metal in the hearth in a molten condition.
Regenerative burners operate as a duel burner unit or as a pair, i.e., burner “A” and burner “B”. While burner “A” is firing, the media in its media box is releasing stored heat to the combustion air entering the furnace to elevate the temperature of the combustion air. The combustion air flows through the media in the media box to the burner head to mix with the gas or oil for combustion in the furnace. At the same time, burner “B” is being utilized as an exhaust system for the combustion hot waste gasses. An exhaust fan draws these hot waste gasses through the burner head of burner “B” and through the media in the burner “B” media box, where the hot waste gasses elevate the temperature of the media and the media bed lining. Once the exhaust gasses downstream of the media box reach a predetermined temperature, which usually takes about 40 to 60 seconds, a pair of air/exhaust duct cycling valves reverse their positions. This switches burner “A” from the burner firing into the furnace to the burner exhausting out of the furnace, and simultaneously switches burner “B” from the burner exhausting to the burner firing. These air/exhaust duct cycling valves are used for switching and reversing the flow of hot gases and combustion air through the media beds.
Each burner assembly has a burner and a media box containing a media that serves as a heat sink. The media usually takes the form of ceramic alumina spheres about one-inch in diameter. When the burner of one burner assembly operates, the hot exhaust gases that it produces discharge into the furnace enclosure above the molten metal and exhaust through the other burner assembly, passing through the media box of that other assembly. Here, the hot exhaust gasses elevate the temperature of the media as the media absorb heat from the hotter gases. After passing through the media, the hot waste gasses discharge into a lateral duct near the bottom of the media box. Then about 40 seconds later the burner shuts down and the burner of the assembly through which the hot gases formerly discharged ignites, the flow of hot gases reverses and combustion air flows through the furnace enclosure. The combustion air for that burner passes through the hot media in the media box for that burner assembly where the temperature of the combustion air is elevated as the media release their stored heat into the cooler gases. Hence, the burner operates more efficiently. Of course, the hot gases from the furnace enclosure now flow out of the idle burner assembly and elevate the temperature of the media in the media box of that assembly. The burners of the two burner assemblies alternate in supplying hot gases to the furnace enclosure, so that the molten metal within the hearth is continuously subjected to hot gases.
During this process, a dross develops over the surface of the molten metal in the hearth that contains various contaminants, such as salts and oxides of aluminum, which the hot exhaust gases pick up. As the gases flow through the media in the media boxes of the two burner assemblies, they deposit some of those contaminants onto the media. These deposits will eventually clog the media. Hence, from time to time each media box is detached from the burner and the lateral duct to which it is connected and taken to a remote location where the media are cleaned and otherwise reconditioned. This is a time-consuming procedure that traditionally requires removing bolts from hot flanges where the burner and the lateral duct couple to the media box and then maneuvering the heavy media box away from the burner and duct without damaging either.
It is therefore desirable to provide a burner assembly in which the media box is adapted to rapidly disconnect from and reconnect to the burner and duct associated with high a temperature furnace. The burner assembly of the present invention overcomes the problems described above and provides significant benefits over existing configurations.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.